The modulator input - usually a sung or simpjy spoken voice - is analyzed with respect to its spectral content, which is then applied to the other sound source. The latter may be any externally supplied signal ranging from pink noise, synth pads, guitar or even drums.

Alternatively, there is an internal, MIDI driven synth which is optimized for best speech reproduction fidelity. You can blend the high frequencies with noise for more natural sounding plosives and fricatives. Threre is also a noise gate, a compressor and a stereo reverb on board.